As a distance measuring device that calculates a distance between an own device and a target in a noncontact manner, a time-of-flight (TOF) distance measuring device is provided. The time-of-flight distance measuring device emits modulated light (distance measuring light) modulated by a pattern having a repeating period to a space and receives incident light including reflected light of the modulated light reflected by the target. The time-of-flight distance measuring device stores an electric charge according to the received incident light in a plurality of storage capacitors while distributing the electric charge by using a plurality of modulation switches, and the time-of-flight distance measuring device calculates the distance between the own device and the target by using a sampled value (for example, see Patent Literatures 1 to 4).
In the time-of-flight distance measuring device, when the distance between the own device and the target is short or when the target is formed by an object having a high reflectance, the reflected light with high intensity is received. On the other hand, when the distance between the own device and the target is long or when the target is formed by an object having a low reflectance, the reflected light with low intensity is only received. Thus, in the time-of-flight distance measuring device, a large dynamic range (for example, 80 dB or more) is required. In particular, in a case in which the device is mounted on a vehicle, when the distance between the own device and the target is short in a state in which at least one of the own device and the target (a person, a vehicle, a wall or the like) is moving, it is required to calculate the distance frequently (to increase a frame rate) in order to avoid collision with the target. That is, it is necessary to achieve both of the large dynamic range and the high frame rate.
It is difficult to achieve the dynamic range of 80 dB or more in a normal pixel, and therefore multiple exposure (a plurality of times of exposure) is necessary to be performed. However, when the multiple exposure is performed in series, exposure time becomes longer and therefore tracking performance against the moving target is deteriorated. Relating to the viewpoint, a method for grouping a plurality of pixels within a plane and changing the exposure time by group is disclosed (for example, see Non Patent Literatures 1 and 2).